I have been thinking that 2x GTX1070 gfx cards may be the go rather than one GTX1080.
Not much of a price difference but great exporting and rendering performance gains according to
This would be with a new Intel Core i7 6950X system and 64 GB Ram
Anyone have any thoughts on this
premiere can use dual gpu, but you may want to check any other software you plan on using. if you have something that only works with one gpu the gtx 1080 might make more sense. normally a single gtx 1070 or 1080 would be fine with the 10-core, but if you are working with red raw media or using other software that needs more gpu power the dual gtx 1070 might may make more sense.
from that puget article it appears the dual gpu was only a big help when rendering previews.
Dual GPU Render Previews:
In the case of rendering previews, we saw about a 40% increase in performance on the Core i7 system.
Dual GPU Export 4k:
Unfortunately, this time dual GPU was only about 10% faster on the Core i7 system.
Go with the single GTX 1080. Premiere Pro only uses one GPU for real-time timeline processing. While 2 cards would improve your render times for exports to DVD format (one's enough for exports to 4k, Blu-ray, etc.), that's not likely to help you much of the time, if at all.
The only real use for dual GTX cards for most editors any more would be those that are using Resolve and if you ever do that, you'll want two (or more!) of the biggest, baddest GTXs you can afford (not likely the 1070 for the price point of your planned build).